Yes, as John S says, the intercooler is in the air inlet circuit AFTER the turbocharger. It is not fitted to all turbo engines, only high performance ones. It's main purpose is to cool the air and so increase its density in order to pack more of it into the cylinder, though of course this will help cool the valves etc as well.
The reason for intercoolers not being fitted to all engines is their unit cost, the cost of plumbing and the extra load on the cooling circuit where they are water-cooled (or the extra air-moving cost where they are air-cooled).
There can also be instances where intercoolers work in reverse, where the engine coolant is at a higher temperature than the air leaving the turbocharger, say when cruising after a hard climb. This means that the inlet air is being heated rather than cooled and this is not ideal. Circuit switching to overcome this has been looked at by Volvo and others but I don't know of any instances where this has been fitted - the on-cost is probably not justified.
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Many thats to all who have left a message here are some things that may need answering in regards to previous messages. I believe my engine has a turbo as standard but the more powerful version of my engine (same engine but with intercooler and bigger injectors). The problem with the engine is that it has a large plastic panel over it which means that looking at detail at the engine is impossible. One last thing I have looked at the running in of the engine at this site and am trying to keep to it however my cars manual recomends no more than 2500 rpm for 750 miles and then it will be run in, the dealer said that there was no run in period, no one can seem to give the same details best just to stick to HJ recomendation I believe
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Just a thought guys on what you were explaining about the purpose of an intercooler.. I wonder what would happen if you took a cold supply from the air con and fed it into the engine, i.e. super cooled high density dehumidified air.. would it be of any performance advantage (ignoring of course the fact that air con will reduce the performance somewhat).....
S.
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SVPworld (incorporating PSRworld)
www.svpworld.com
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I guess in theory it would improve the performance. I remember reading somewhere about some Jap performance cars (I think it was an Impreza) where there is a device that squirts water into the intake at the touch of a button.
This water cools down the air and therefore makes it denser. I'm not sure if the oxygen in the water also helps the burn process...
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IIRC, water injection has been used on various aero engines, both jet and piston.
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Yes, water injection is a very old idea and is not generally favoured because of its corrosive (or erosive?) effect within the engine.
As an alternative, for diesels in particular, fuel/water emulsions have been investigated again and again over the years. The main problem has been in getting an emulsion that won't separate during the engine combustion process and, as with water injection, shorten the life of the engine. Several companies have claimed to have achieved this and have patented their mixing systems, but I think we should reserve judgement on this.
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If you want injection nitrous oxide is the one to go for!!
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If you want injection nitrous oxide is the one to go for!!
That's a bit of a laugh!
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Dizzy
The water injection systems I'm aware of are those used to cool the inlet air to Gas Turbines in hot countries. In these systems full evaporation is achieved before the compressor, absorbing latent heat of evaporation, and this shouldn't have a damaging effect on the engine. RH should remain below 100%.
Unless IC engine systems inject much greater quantities of water for it to evaporate in the combustion chamber, then there shouldn't be any damaging effect. I wonder if damage is caused by system failure rather than design injection levels. For an engine running on high quality fuel, it shouldn't need water in the combustion chamber - the main benefit is pre-cooling to achieve maximum air mass in the combustion chamber.
Otherwise, it may be that these high injection rates are designed to reduce maximum combustion temperature, and reduce pre-ignition, but it would be a very difficult to achieve a balance between improvement in performance and loss of output due to overcooling.
Very stable emulsions are achieved - the classic example is orimulsion, the bitumen/water emulsion marketed by Bitor. This is stable in storage for several years. Not surprisingly the emulsifier is a closely guarded trade secret. Emulsions need careful design in respect of pumping systems, as high shear is an excellent way of separating the emulsion. With these heavy fuels the water particles in the combustion process do have a benefit. The rapid boiling and expansion of the water in the combustion process disrupts the fuel particles, reducing their size, and improving their combustion.
Regards
John S
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John,
It was only IC engines that I was thinking of, not gas turbines, and I was repeating what I had picked up from elsewhere long ago. I haven't been directly involved in water injection so I cannot put forward any scientific arguments for or against.
When it comes to fuel/water emulsions, I do have a bit of direct knowledge on this in relation to diesel engines but am not at liberty to discuss this in fine detail. However, you were not far off the mark of what I had in mind, to which I would add ...
The main purpose of fuel/water emulsions in diesel engines is to reduce emissions of nitrous oxides (NOx) and particulates. Carbon build-up may also be reduced, leading to better maintenance of engine efficiency. There are therefore strong incentives for reliable emulsions to be marketed, and for tax reductions to be given to encourage its use, but this can only follow full development and validation.
Many proposed fuel/water emulsions suffer separation as they pass through the injection and combustion systems of engines and this can lead to damage. A hyperthetical example is that high velocity water impingement on cylinder walls could break up the surface oil film. Remember, we are now in the era of 1600 to 2000 bar (23000 to 30000 psi) injection pressures, which brings us close to your comment about high shear causing separation.
An interesting subject and I think we will see much more of it in the not-too-distant future.
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Dizzy
Yes, I wondered if thermal NOx was the problem. In that case particulate water in the combustion chamber, rather than pre-cooling with vapour, would be a benefit by reducing peak combustion temperatures.
I can imagine the deposition in the combustion chamber would be reduced with emulsion firing. I once had a Mini which suffered a cracked cylinder head, allowing coolant into one cylinder. When the head was removed the faulty cylinder was obvioous - the combustion chamber was spotless!
Regards
John S
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Actually I wasn't referring to injecting water into the injection, quite the opposite infact. Air con provides dehumidified chilled air, ideal I would have thought for the engine.
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SVPworld (incorporating PSRworld)
www.svpworld.com
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Yes, we drifted away from your neat idea, svpw. I can't think it through at the moment but sending pre-chilled air into the engine sounds good, though I'm sure there must be drawbacks. Perhaps the volumes required would need a very large and power-consuming air-con unit.
Hey, how did we get into all this from Edd's simple 'Clio running in' question?
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"Hey, how did we get into all this from Edd's simple 'Clio running in' question?"
via "Intercoolers".
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It makes for more interesting reading and anyway it seems that the other question si wrote have been answered. Let the thread run on.
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\"Many proposed fuel/water emulsions suffer separation as they pass through the injection and combustion systems of engines and this can lead to damage
An interesting subject and I think we will see much more of it in the not-too-distant future.\"
See news.bbc.co.uk/1/hi/england/2265860.stm
(sorry I\'ve forgotten how to do links)
[you\'ve miraculously remembered. M.]
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Brian,
I read the story with interest and I hope the inventor is successful. Interesting that his emulsion came about by trying an additive that he just happened to have in his garage whereas several large players have spent millions and still not perfected a stable emulsion.
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